Animation advice please (sliding pipes with handles)
Shapekeys

Would consider using shapekeys for the handles.   With two shapekeys fully flexed and fully straight.

For example sake have made the rest of the mesh into shapekeys, however could use hooks or constraints to move cylinders, but what matters here is getting the handle flex.

To open close handle is now only a matter of adjusting flex shape value.




Model a curve in the shape of full flex out.  I've used a simple 2 point bezier here
For example sake add the default cube, adjust the dimensions to
better suit.
To this add an array modifier, set to fit the  curve, and then a
curve modifier using same.  May need to tweak the curve scale, and / or cube scale, slightly to make sure it's a nice fit, ie how the last one fits the curve 


We now have the flexed strap.


Apply the array modifier, to make it one mesh instead of an array of
items, and then apply the curve modifier as a shapekey  You will
notice the base shapekey is a flat line made up of how many of our
unit items fit the curve.
In edit mode moved the strap up, then adding a mirror modifier on y (top view in examples)
axis will give two handles.
In edit mode with Basis shape key selected, Add the two cylinders,
and adjust there position to match there attached ends. Change to
bent shapekey and do same.



Very quickly mashed together result from default cube and cylinders only.

Locating the pins.

Before I consine file to the ether, added this re using flexible bands to locate other objects



To locate pins that go thru the start and end element of strap

Select top and bottom face of where the pin goes thru and create and assign a vertex group for each end.

Added a pin object (mirrored in y same as flex). A copy location constraint on the pin to the flex, to the vertex group locates it.  This can be exended for the pistons.